Cellular telecommunications networks include a base station configured to transmit wireless signals over a coverage area to several User Equipments (UEs). Traditional cellular networks included base stations transmitting over a large coverage area, typically several kilometers squared, and serving many thousands of UEs. However, the trend in cellular networks has been to increase the density of base stations per unit area, each with a smaller coverage area and serving fewer UEs. These high density cellular networks have a relatively high capacity and offer users greater data rates. The small-scale base stations are often known as small cells, and include picocells, microcells, metrocells and femtocells (depending on their coverage area).
In 4th Generation cellular networks, such as Long-Term Evolution (LTE), these small cells are also known as Home evolved NodeBs (HeNBs). Unlike traditional cellular networks in which the base stations are installed and configured by technical experts of Mobile Network Operators (MNOs), these HeNBs will likely be installed by end-users and will rely on distributed Self-Organizing Network (SON) algorithms for self-configuration. The task of these distributed SON algorithms is to automatically configure each base station in the network with configuration parameters that optimize that base station's coverage and capacity, whilst trying to minimize any interference caused on other base stations in the network. The inputs to these SON algorithms are typically locally measured properties (such as the results of a radio environment scan) rather than those distributed between base stations by control signaling.
A useful input parameter to these SON algorithms is the distance between the HeNB and its closest neighboring base station. If two HeNBs include geolocation technology (such as a Global Navigation Satellite System, GNSS, module), then it is able to calculate this distance by comparing their respective locations. However, this is not an optimal solution as the GNSS module generally does not work indoors, increases the unit cost of the HeNB, and relies on the distribution of this data and therefore an increase in control signaling. Furthermore, this distance may become inaccurate if one base station is moved, and thus requires periodic recalculation (which, for GNSS geolocation, requires substantial processing). For HeNBs without geolocation technology, it is difficult for a HeNB to determine its distance to its nearest neighbor from local measurements alone, as it is difficult to distinguish one neighbor transmitting at low power from a more distant neighbor transmitting at high power.